DPP-IV (EC 3.4.14.5) is a serine protease that preferentially hydrolyzes an N-terminal dipeptide from proteins having proline or alanine in the 2-position. DPP-IV is believed to be involved in diabetes, glucose tolerance, obesity, appetite regulation, lipidemia, osteoporosis, neuropeptide metabolism and T-cell activation, among others. Accordingly, administration of DPP-IV inhibitors in vivo prevents N-terminal degradation of substrate peptides, thereby resulting in higher circulating concentrations of such peptides, and therapeutic benefits associated with such elevated concentrations.
DPP-IV has been implicated in the control of glucose homeostasis because its substrates include the incretin peptides glucagon-like peptide 1 (GLP-1) and gastric inhibitory polypeptide (GIP). Cleavage of the N-terminal amino acids from these peptides renders them functionally inactive. GLP-1 has been shown to be an effective anti-diabetic therapy in Type 2 diabetic patients and to reduce the meal-related insulin requirement in Type 1 diabetic patients. GLP-1 and/or GIP are believed to regulate satiety, lipidemia and osteogenesis. Exogenous GLP-1 has been proposed as a treatment for patients suffering from acute coronary syndrome, angina and ischemic heart disease.
Administration of DPP-IV inhibitors in vivo prevents N-terminal degradation of GLP-1 and GIP, resulting in higher circulating concentrations of these peptides, increased insulin secretion and improved glucose tolerance. On the basis of these observations, DPP-IV inhibitors are regarded as agents for the treatment of Type 2 diabetes, a disease in which glucose tolerance is impaired. In addition, treatment with DPP-IV inhibitors prevents degradation of Neuropeptide Y (NPY), a peptide associated with a variety of central nervous system disorders, and Peptide YY which has been linked to gastrointestinal conditions such as ulcers, irritable bowel disease, and inflammatory bowel disease.
In spite of the early discovery of insulin and its subsequent widespread use in the treatment of diabetes, and the later discovery of and use of sulfonylureas (e.g. chlorpropamide, tolbutamide, acetohexamide, biguanides (e.g., phenformin), metformin, thiazolidinediones (e.g., rosiglitazone), and pioglitazone as oral hypoglycemic agents, the treatment of diabetes remains less than satisfactory.
The use of insulin, necessary in Type 1 diabetic patients and about 10% of Type 2 diabetic patients in whom currently available oral hypoglycemic agents are ineffective, requires multiple daily doses, usually by self-injection. Determination of the appropriate dosage of insulin necessitates frequent estimations of the glucose concentration in urine or blood. The administration of an excess dose of insulin causes hypoglycemia, with consequences ranging from mild abnormalities in blood glucose to coma, or even death.
Treatment of Type 2 diabetes usually comprises a combination of diet, exercise, oral agents, and in more severe cases, insulin. However, the clinically available hypoglycemics can have side effects that limit their use. A continuing need for hypoglycemic agents, which may have fewer side effects or succeed where others fail, is clearly evident.
Poorly controlled hyperglycemia is a direct cause of the multiplicity of complications (cataracts, neuropathy, nephropathy, retinopathy, cardiomyopathy) that characterize advanced Type 2 diabetes. In addition, Type 2 diabetes is a comorbid disease that frequently confounds hyperlipidemia, atherosclerosis and hypertension, adding significantly to the overall morbidity and mortality attributable to those diseases.
Epidemiological evidence has firmly established hyperlipidemia as a primary risk factor for cardiovascular disease (CVD) due to atherosclerosis. Atherosclerosis is recognized to be a leading cause of death in the United States and Western Europe. CVD is especially prevalent among diabetic subjects, at least in part because of the existence of multiple independent risk factors such as glucose intolerance, left ventricular hypertrophy and hypertension in this population. Successful treatment of hyperlipidemia in the general population, and in diabetic subjects in particular, is therefore of exceptional medical importance.
Hypertension (high blood pressure) is a condition that can occur in many patients in whom the causative agent or disorder is unknown. Such “essential” hypertension is often associated with disorders such as obesity, diabetes, and hypertriglyceridemia and it is known that hypertension is positively associated with heart failure, renal failure, and stroke. Hypertension can also contribute to the development of atherosclerosis and coronary disease. Hypertension, together with insulin resistance and hyperlipidemia, comprise the constellation of symptoms that characterize metabolic syndrome, also known as insulin resistance syndrome (IRS) and Syndrome X.
Obesity is a well-known and common risk factor for the development of atherosclerosis, hypertension, and diabetes. The incidence of obesity and its related sequelae is increasing worldwide. Currently, few pharmacological agents are available that reduce adiposity effectively and acceptably.
Osteoporosis is a progressive systemic disease characterized by low bone density and microarchitectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture. Osteoporosis and the consequences of compromised bone strength are a significant cause of frailty, and of increased morbidity and mortality.
Heart disease is a major health problem throughout the world. Myocardial infarctions are a significant source of mortality among those individuals with heart disease. Acute coronary syndrome denotes patients who have or are at high risk of developing an acute myocardial infarction (MI).
Though there are therapies available for the treatment of diabetes, hyperglycemia, hyperlipidemia, hypertension, obesity, and osteoporosis there is a continuing need for alternative and improved therapies.
Various indications for DPP-IV inhibitors are discussed in Augustyns, et al., Curr. Medicinal Chem., 6, 311 (1999); Ohnuki, et al., Drugs of the Future, 1999, 24, 665-670 (1999); Villhauer, et al., Annual Reports in Medicinal Chemistry, 36, 191-200 (2001); Drucker, Expert Opin. Invest. Drugs, 12, 87-100 (2003); and Weideman, et al., Curr. Opin. Invest. Drugs, 4, 412-420 (2003).
Orally administered compounds that inhibit DPP-IV have recently been prepared, such as those disclosed in International Application WO 02/14271.
DPP-IV inhibitors, such as those disclosed in WO 02/14271, are believed to act by inhibiting the degradation of the natural hormones, GLP-1 and GIP. Therefore, it is important that a suitable concentration of the DPP-IV inhibitor be available in plasma to inhibit DPP-IV coincidently with the secretion of these GLP-1 and GIP hormones. To achieve such plasma concentrations, it is preferred that the DPP-IV inhibitor compounds maintain a higher plasma concentration over time than that which would be expected for other DPP-IV inhibitor compounds, such as those disclosed in WO 02/14271.
Therefore, what is needed is an orally administered DPP-IV inhibitor compound that has equivalent or better DPP-IV inhibitory activity and that maintains a higher plasma concentration over time.